Method of conducting catalytic reactions



Jan. 1,5, 1946. c'. THOMAS 2,392,957

I METHOD 0F CONDUCTING CATALYTIC REACTIONS Filed Aug. 30, 1943 .7%yar/zeg.-

trentenne. 1s, 194e manon or conoscente sername EMONS Charles L. Thomas,Riverside, Ell., assigner to Universal Oil Products Company, acorporation of Delaware Chicago, lll.,

lapplication August so. 194s, serial No. 500,53@

, (ci. 19e-s2) (i Claims.

tact material upon which deleterious heavy com- Ibustible products ofthe conversion reaction are deposited and from which said deposits areperiodically removed in an exothermic regenerating step to restore theactivity of the subdivided solid material and, when desired, store heattherein for subsequent use in' conducting the conversion reaction.

The improved process herein provided is of the general type known as xedbed operation in the sense that conversion of the fluid reactants in thepresence of the active catalyst or contact material and regeneration ofthe resultlng contaminated catalyst or contact material are accomplishedalternately in the same reaction vessel. Preferably, in this processY asin typical iixed bed operation, lavo or more reaction vessels areemployed alternately in processing and regeneration service .so thatboth operations may be conducted continuously.- The improvedmode ofoperation herein provided diiers from conventional ixed bed practice inthat the mass of subdivided solid materials undergoing regeneration aremaintained in a turbulent duid-like state but, preferably, while beingemployed to promote the conversion reaction, the mass or :bed ofpreviously regenerated subdivided solid particles is maintained in arelatively compact condition.

To achieve fluidization of the mass of sub divided solid particlesundergoing regeneration, air or other oxidizing gas employed for burningcombustible contaminants therefrom and resulting combustion gases arepassed upwardly through the mass at avelocity regulated to bring aboutthe lphenomenon known as hindered settling. This is a result of thelifting action of the oxidizing gas and combustion gases workingopposite to the force of gravity on the subdivided solid particles and acondition of turbulence resembling that of obtained inthe mass.

The regenerating step of the present process is further characterized inthat a distinct twophase condition exists in the regenerating zone. Theturbulent duid-like bed of solid particles is relatively dense andcontains a. `considerably higher concentration of solid particles thanvthat -which would prevail in the absence of their pronounced hinderedsettling (i. e., thesolid particle concentration in the iluid bed'` ismaterially greater than that which would obtain in an operation wherethe solid particles are carried along in the gas stream without materialreverse' A s movement or back ilow of the solid particles).

Above the iluid bed in the regenerating zone a. ylight phase conditionprevails in which the solid particle concentration is materially reduceddue to the reduced amount or substantial absence of hindered settling inthis region, and a relatively sharp line of demarkation is maintainedbetween the dense phase fluid :bed and the light phase' r outgoing gasstream and eect a major separation of solid bed.

The iluidized bed mode particles from gases in vthe iluid of operationin the regenerating step has pronounced advantages.

a boiling liquid is Due to its iluid-like turbulent condition thetemperature is substantially uniform throughout the bed. This avoids thelocalized excessively high temperatures or hot spots encountered whenlit is attempted to accomplish regeneration in a compact bed and permitsthe use of a higher average temperature for regeneration. Thus, moreheat may he stored in the regenerated mass and subsequently used inconducting the endothermic conversion reaction 'without the danger ofexcessive local heating in the regenerating step. With most catalysts atemperature above 1300 F. or thereabouts at any point in the bed, andin. some cases even lower temperature, will result in permanentimpairment or destruction of the activity of the ca s -exposed thereto.

Another advantageous feature of the invention resides vin maintaining adistinct dense phase level in the regenerator at a point well beneaththe combustion gas outlet. Thus, good separation of the solid particlesfrom the outgoing gases is obtained in the' 4regeneratox so that thecatalyst vor contact material is retained therein much. the same as inan operation employing a relatively compact bed. The further preventionof catalyst loss in the outgoing regenerating gases is readily achievedby the use of relatively simple separating equipment, such as that ofthe centrifugal or cyclone type, for example. 'Ihis good separation andretention of solid particles in the regenerating zone can beaccomplished with considerably higher linear sas velocities than thoseusable in a compact bed through which the oxidizing Also, due toturbulence and substantially uniform temperature distribution in the uidbed, un-

diluted air can ordinarily be employed as the oxidizing gas rather thanair prediluted with combustion gas or other relatively inert gas as isusually necessary when the catalyst particles undergoing regenerationare in the form of a compact or non-fluidized bed. This also permits theume of outgoing hot gases is reduced. l

It was previously thought that the use of a fluid-like bed in thereaction step would likewise be benecial by virtue of the goodtemperature distribution obtained under the turbulent flow conditionsand because of the higher permissible charging stock capacity for areactor of given diameter and length due to the use of higher linearvelocities than can be employed when the reactants are passed upwardlythrough a relatively compact bed. On the contrary, my investigationshave demonstrated that improved results with respect to the yield andquality of the desired pr'oducts are obtained by employing a relativelycompact catalyst bed in the reaction step as compared with the resultsobtained under otherwise similar operating conditions while employing auidized bed, and these improved reout sacrifice of charging stockcapacity In the voluminous art on the catalytic co version of fluidreactants and in the extensive.

lretention of more heat in the bed, since the volsults can be achievedin the present -process withand to which I have access, I was unable tond l any basis for my presumption that improved results would beobtained by the use of a compact bed in the reaction step as comparedwith those obtained under otherwise similar operating conditions whileusing a fluidized bed. Therefore, exploratory experimental work wasnecessary. The results of pertinent portions of this work are given inthe subsequent examples andall of the results lead to the conclusionthat an improvement in both yield and quality of the desired products isobtainable bythe use of a relatively compact bed in the reaction step.This is believed to be due to improved contact between the r reactantsand the catalyst in the compact bed as compared with a fluidized bed,but since I know of no accurate or satisfactory method of directlymeasuring intimacy of contact in such an operation, this belief cannotbe 'conclusively proven. However, visual inspection of the conditionsprevailing 4in a iiuid-like bed of subdivided solid contact material inglass models tends to verify the belief that the iluidizing medium` isnot uniformly contacted with the solid particles. Relatively large gaspockets or bubbles tend 'to form at a relatively low point in the iuidbed and move upwardly therethrough without subdivision or dispersion inthe bed under the conditions of linear gas velocity, particle size ofthe contact material, etc., ordinarily employed in iiuid bed operation.

While intimacy and uniformity of contact between the .subdivided solidmaterial and the fluidizing medium is important in the reaction stepwhere the iiuidizing medium employed comprises the reactants to beconverted, itis of materially less significance and relativelyunimportant in the regenerating step where the uidizing medium is air orother oxidizing gas. In otherwords,

tact material.

such as above mentioned.

any improvement in contact which might be obtained by the use of acompact bed in the regenerating step is far outweighed by the beneiitswhich result from the use of a iiuid-like bed in this step.

In the preferred embodiment of the invention, although this feature isnot essential in itsbroader aspects, the reactants to be converted andthe resulting iiuid conversion products are passed downwardly throughthe relatively compact bed `of subdivided solid catalyst or contactmaterial in the reaction step. This permits the use of higher linearvelocities for the fluid reactants and conversion products than could beemployed without obtaining fluidization of the bed with upward flowtherethrough and permits charging stock-capacities comparable to thosewhich can be employed in a uidized bed without the use of a re'- actionvessel of excessively large diameter or horizontal cross-section.

In order to achieve good i'luidization of the bed in the regeneratingstep and avoid, in the reaction step, an excessive degree of compactionwhich would hinder flow or give a high pressure drop with down-nowthrough the bed, I preferably employ catalyst or contact material ofrelatively uniform, graded particle size Whichis larger than commonlyused in fluid bed operations and smaller than that commonly used inconventional fixed bed operations. While this is important, it is notconsidered essential to the successful operation of the process and theparticle size selected will depend to some extent upon other operatingvariables. As an example, in' the catalytic cracking of hydrocarbon oilemploying a siliceous cracking catalyst, such as a composite of silicawith one or more metal oxides, such as alumina, zirconia and magnesia, agood average range of catalyst particle vsize to employ is 40 to 100mesh, or thereabouts.

The features of the invention will be found' advantageous as applied toa wide variety of reactions in which fluid reactants are converted' inthe presence of a mass of subdivided solid particles which becomecontaminated and require regeneration regardless of whether thesubdivided solid material has a catalytic iniiuence on the reaction oris employed as a relatively inert con- In its broader aspects theinvention is therefore limited only to reactions o f this general classin which regeneration of the mass of solid particles is accomplishedwhile the latter is in a fluid-like state and in which conversion ortreatment of the uid reactants is accomplished in the presence of a massof the regeneratedlsolid particlesmaintained in a relatively compactcondition. However, the invention is more particularly directed tohydrocarbon conversion reactions and specifically contemplates the useof the features of the invention in the catalytic cracking of normallyliquid or normally gaseous hydrocarbons and the reforming of lighthydrocarbon distllates, such as gasoline, naphtha and the like, in thepresence of a siliceous cracking catalyst The invention alsocontemplates the dehydrogenation of normally gaseous or normally liquidhydrocarbons in the -presence of a dehydrogenating catalyst such asinvolving various combinations of cracking or reforming, dehydrogenationand aromatization.

Although not strictly limited to endothermic operation in the reactionstep, the features of the' invention are particularly advantageous asapplied to an operation in which the reaction is either endothermic orso nearly thermally bal'- anced that radiation losses necessitatessupplying heat to the reaction zone other than that contained'in theincoming stream of fluid reactants. In such operations heat stored inthe mass of catalyst or contact material during its exothermicregeneration is given up in the reaction step and supplies all or asubstantial portion of the heat necessary for conducting the latter. o

In operations of the type to which the above invention is addressed,wherein the same vessel is alternately employed in regenerating andprocessing service, the supply of heat to the reaction from the mass ofregenerated sub-divided solid material results in a gradual decrease inthe temprocess and the severity and' rapidity of temperature changesjtc.which it is subjected.

lAnother method of storing additional heat' in themas of subdividedsolid particles undergoing regeneration for subsequent use in conductingthe conversion reaction is to supply to and burn fuel in theregenerating step other than the combustible. deposits formed on solidparticles in the processing step and this feature may be utilized eitheralone or iniconiunctionv with the use of inert, subdivided solidmaterialf asl above deperature of the latter as the operationprogresses.

Thus, the average reaction temperature during the processing st ep issomewhere betweenthe satisfactory low temperature and high temperaturelimits, and when the temperature of the-bed recedes to the lower limitfor satisfactory operation, the bed must be regenerated to storeadditional heat therein and is put back into processing service at atemperature approaching the satisfactory maximum. In some operationsthis would necessitate relatively short operating cycles and toofrequent regeneration. Also, in some operations, notably the catalyticdehydrogenation of normally gaseous hydrocarbons, such as butane,

for example, and the catalytic reforming of gasoline to improve itsoctane rating, the quantity of combustible contaminants deposited on thecatalyst during the processing step will not furnish and store in thecatalyst, upon their combustion in the regenerating step, suiiicientheat to satisfy the requirements of the endothermic conversionreaction.' y o As a special feature of the invention in operations suchas above mentioned, the heat stored in the mass of subdivided solidmaterial during its regeneration may be increased by one or acombination of methods so as to retain suilcient heat in the bed tosatisfy the requirements of the reaction step and, when' desired, toprolong the l,period of operation between regenerations. One method ofaccomplishing this comprises the use, 'with the catalyst, of relativelyinert subdivided solid material having a greater heat capacity per unitvolume than the catalytic material, to improve the heat storing capacityof the bed. Preferably, the relativelynert material is in the form ofdiscrete particles approximately corresponding in size or in iluidizingcharacteristics to the catalyst particles. .However, I also contemplatethe disposition of catalytic' material on the surface of relativelyinert subdivided solid particles of good heat capacity or compositingthe inert material and the catalyst to form the particles of contactmaterial employed. In general, ma-l calcined clays or shales, quartz andthe like are suitable for use as the inert' terlals such as kaolinmaterial andin some instances various ores, metals, alloys, metal oxidesor other solid metal compounds may be employed.

tion to be conducted, the temperatures to which the subdivided solidmaterial is subjected in the The selection will, of course, depend uponthe particular reacinvention above mentioned, it is also characterlistic of the prsent process that, as a result of the substantiallyuniform temperature distribution accomplished by fluidization of the bedin the regenerating step, a higher average regenerating temperature canbe employed than it is safe to use in regenerating a relatively compactbed` of catalyst which is susceptible to damage at high temperature.Also," by using -undiluted air as the iiuidizing and-oxidizing medium inthe regenerating step, which is permissible on account of the iiuidizedcondition of the bedv and the resulting good temperature distribution,less heat is carried from the regenerating step in the outgoing gaseousproducts as compared with that the air employed for combustion withrelatively' large quantities of inert gas. Thus, even without the use ofeither of the aforementioned special features of the invention, it ispossible to store more heat yin the mass of subdivided solid materialundergoing regeneration than could be safely stored while regeneratingthe same mass in the form of a relatively compact bed.

It will, of course, be understood that the features of the inventionwhich permit the storage of additional heat in thebed during itsregeneration will be useful in operations where the bed is maintained ina Huid-like condition during the reaction and the regenerating steps. -Aprocess of this type, which is more fully described in my aforementionedco-pending application Serial Number 426,304, is therefore entirelywithin the scope of the invention. I

In some other operations, such as, for example, the catalytic crackingof high carbon-forming oils and catalytic aromatization, the deposits ofcombustible conversion products formed on the catalyst particles duringthe processing-step are materially in excess of those required tothermally balance the processing and regenerating steps. In suchinstances it is desirable `toabstract addition to the heat carried fromthe regenerating step in' the outgoing streamvof spent or partiallyspent regenerating gas'. condition of the bed inthe regenerating stepthis can conveniently be accomplished in the process provided by theinvention by establishing a' local cycle of. catalyst particles from arelatively high region,Y in the iluid bed through a suitable cooler,such as, for example, a waste-heat boiler or other convenient form of.heat exchanger, back into a relatively low region in the bed. Thisfeature obviates the use of a complicated and costly heat exchange'typeof regenerating vessel.

'I'he accompanying drawing diagrammatically illustrates one specificform of f apparatus in which the improved process provided.c by theinvention may be conducted.

Due to the fluid-like illustrated comprises substantially cylindrical,vertically disposed. reaction and regenerating vessels I and 2, eachhaving a substantially conical lower head and an upper head in which the5 respective cyclone separators 3 and 4 aremounted. Each of the vesselsis also equipped with a screen or other suitable perforate membercapable voi' retaining the particles of subdivided solid materialcomprising the beds in th vessels. l

These perforate members are indicated at and Y l in the respectivevessels i and 2 and are preflpermits continuous operation of the processby alternate use of vessels I and 2 in processing andregeneratingservice. This is accomplished by manipulation of the variousvalves, as will be later described. A main inlet line 1 for theinicoming fluid reactants to be converted communicates through thebranch lines 8 and 9, having the respective valves. II and Ii, with theupper portion of the respective vessels I and 2, Lines I2 and I2 at thebottom of the respective vessels- I and 2, establish communicationbetween the spaces provided beneath the perforate members l and l,through the respective branch lines I4v and I5, containing therespective valves I6 and 30 I1, with an outlet header I8 for the fluidproducts of the conversion reaction. Lines I2 and I3 also communicatethrough the respective branch lines 2| andv 2i., containing therespective valves 22 and 2l, with the inlet line I9 for the air or other35 oxidizing gas employed to fluidize the bed in the regenerating zoneand effect combustion of the contaminated deposits on the subdividedsolid material. The branch outlet lines 24 and 25 from the respectivecyclone separators 3 land 4 com- 40 reduced, by the liberation ofthe'heat therefrom to the reaction taking place in this zone, to a valuemunicate through the respective valves 26 and 21 with the main outletline 29 for gaseous prod- `ucts of the regenerating operation. Lines and2| lead from a suitable point in the upper portion of the respectivevessels i and 2 to the catalyst 4:,

cooler 33, and the lines 34 and 35 lead from the catalyst cooler throughthe respective valves 36 and I1 to a lower 'point in the vessels` I and2 above the perforate members 5v and 6.

, The arrows in the drawing indicate the direction of iiow through thevarious lines when vessel I is being employed as the reaction zone andvessel 2 is being employedas the regenerating zone. During this stage ofthe operating cycle, valves It, I8, 23 and 21 are open and valves II,I1, 22 55 and 26 are closed, while valve 3i may be opened and valve 38vclosed if the circulation of catalyst is desired through cooler 33.During this stage of the operation air or other oxidizing gas isadmitted to and 'flows upwardly through vessel 2 in,^ o

contact with the mass of previously contaminated i catalyst in this zoneto burn the combustible deposits therefrom and the upward velocity o fthe oxidizing gas and resulting combustion gases maintains the bedin aturbulent fluid-like condition. The approximate upper extremity of thedensephase fluid bed is indicated at 28 and a light phase, in which theconcentration of catalyst particles is materially reduced, exists abovethis level. iight phase enter the cyclone separator 4 with the outgoingcombustion gases and substantially all of the entrained solid particlesare separated from the gases in this zone and returned through stand-'pipe 3i to the dense phase fluid bed 4l.. The 75 Entrained catalystparticles from the Referring to the drawing, the apparatus herecombustion gasesfrom separator 4 are directed through line 2li, valve 21and line 29, preferably to suitable heat recovery equipment notpertinent to the present invention and', therefore, not illustrated. l l

During regeneration of the catalyst, as above described, in vessel 2,hydrocarbons or other fluid reactants to be converted are admittedpreferably, but not necessarily, in preheated state through line 1, line8 and valve I0 to vessel I and passed downwardly with resulting iiuidconversion products through the hot relatively compact bed 4I ofpreviously regenerated catalyst, wherein their conversion to the desiredproducts is accomplished with the resulting deposition of deleteriouscombustible conversion products on the catalyst particles. The resultingfluid conversion products are discharged through lines I2 and I4, valveI2 and line I8, preferably to suitable fractionating and recoveryequipment, not illustrated, and, when desired, in case any substantialquantity of catalyst particles escape from the bed 4I through member .5,suitable separating equipment, not illustrated, may be interposed inline I8 or within the conical lower head of chamber -I to recover -theseparticles.

It will be noted with reference to the drawing that une 42, indicatingthe approximate upper extremity of the compact catalyst bed in vessel I,is at a, considerably lower level than line 38, indicating the upperextremity of the iluid bed in vessel 2. This, Aof course, is due to thefact that bed 4I i is in a relatively compact condition, while bed 40 isiiuidized so that with substantially the same weight of catalyst in eachvessel, as the process is preferably operated, the bed in the vesselwhere the conversion reaction is being confvducted occupies considerablyless space than that approaching the lower limit -of the desired rangeof operating temperature, the conversion step is shifted to vessel 2 andthe regenerating step is shifted to vessel I, preferably after vessel Ihas been substantially purged of fluid reactants and conversion productsand after vessel 2 has been substantially purged of oxidizing gas andcombustion gases-such purging being accomplished by any convenient wellknown means, not shown. During that portion of the operating ,cycle inwhich vessel lI is employed as the regenerator and vessel 2 as'the zonein which the conversion reaction is conducted, valvesY I0, I8, 23 and 21are closed and valves Il, II, 22 and 26 are open, the now through thesystem being as would be indicated-by the arrows in a mirror image ofthe drawing.

The catalyst cooler 33, as previously mentioned, is operated for thelocal circulation of catalyst from the fluid bed undergoing regenerationthrough the cooler back into this bed when it is desired -to abstractheat from the regenerating step in addition to that carried from theregenerating zone in the outgoing combustion gases.

As indicated in the drawing, cooler 23 is so displied to thecoolerthrough line 43, wherethrough it passes in indirect contact and heatexchange aeeaesr relation with the stream ci catalyst, particles andfrom which resulting heated fluidis discharged through line dd andval-vc Regulation of the opening through valve GS orl valve 3l, as thecase may be, will control the flow of catalyst through cooler 33 andthis, in conjunction with control of the rate at which cooling fluid issupplied to cooler 33 and its temperature, will regulate the ladditional heat abstracted from the fluid bed undergcing regeneration.When inert subdivided solid material is employed with the catalysty aspreviously explained,`

to increase heat storage in the bed, it may conveniently be mixed withthe catalyst particles plied to theupper portion of the reaction vesseland resultingl oil vapors and gases were passed downwardly through thecatalyst bed which was maintained in a compact condition. The chargingoil, in each case, was suppliedto the reaction Test number Operatingconditions Condition oi bed during processing Condition oi bed duringregeneration Average reaction temperatura Average regeneratingtemperature Operating pressure in reaction zone outl Weight hourly sacovelocity Processing pei-io Products (weight per cent toned on chargingstock) Gasoline (400 F., E. P.)

Catalyst deposits.

riuidi'zed. riunirsi. do Do.

105o Amospheric.` (il) minutes.

C@ and lighter gases-..

Total weight per cent of charging oil converted to lighter and heavierfractions..

` Analysis of gasoline Weight per cent clcns Weight per cent aromaticsWeight per cent paraiiins -lnaphthenos Octane number (A. S. T. M. motormethod) before the operation is started and charged to the two reactionvessels.

One ora plurality of suitable burners indicated at dt and di is providedfor supplying fueland additional air to vessels i and 2 from an exteriorsource when it is desired to augment the heat evolved and store it inthe fluid-like bed of subdivided solid material during regeneration forsubsequent use in conducting the conversion reaction. Any desired typeof fuel may be employed, although gaseous or liquid fuel is ordinarilypreferred.

The following examples are presentative of a series of tests conductedto determine` the Vadvantages of the features of the invention asapplied to the catalytic cracking of hydrocarbon oil.

A synthetically prepared silica-alumina cracking catalyst substantiallyfree of alkali metal compounds and having a particle size ranging fromapproximately 40 to 100 mesh was employed in each of these tests tocrack a Mid-Continent gas oil. An average reaction temperature ofapproximately 950 F. was employed in each case using weight spacevelocities (weight of oil supplied to the reaction zone per hour, perunit weight of catalyst present in the reaction zone) of 1 and 2. 1 and0.5 weights of catalyst were used per unit weight of oil charged to thereaction zone before the catalyst was regenerated (i. e., a processingperiod of 60 minutes between regenerations, in each case). The crackingreaction and regeneration of the catalyst were alternately conductedinthe same reaction vessel. In two of the tests charging oil wassupplied to the lower portion of the reaction vessel and resulting oilvapors and gases were directed upwardly through the catalyst bed duringthe cracking period tomalntain the bed in a turbulent fluid-likecondition. In the other two tests the charging oil was supyIt will benoted from the above tabulation that, under otherwise comparableoperating conditions, when the catalyst bed was maintained in a compactcondition during processing improved results were obtained with'respectto the weight percent of gas oil converted and that the octane ratingand aromatic content of the gasoline were improved. Also, at the higherspace velocity (higher charging stock rate) a higher percentage ofgasoline was obtained based on thel charging v wardly through said body,maintaining said body of catalyst in a uidized' condition during theregeneration period by passing a regenerating gas upwardly therethroughat a linear velocity such that a relatively dense uidized catalyst phaseexists as a result of hindered settling of the i catalyst particles andsaid relatively dense phase is superimposed by a relatively iight phase,withdrawing eiiiuent regeneration gases from said relatively light phaseat a point substantially above the line of demarcation between saidrelatively dense` and relatively light phases, separating the relativelysmall quantity of catalyst particles entrained in said eiuent gases, andreturning the thus separated catalyst to said relatively dense phase. i

2. The improvement as defined in claim l further characterized in thatthe catalyst is employed in admixturewith relatively inert solidkpai'ticlesof higher heat capacity than the cataversion reactioncomprises the catalytic crack- I ing of hydrocarbons.

5. The process of claim 1, wherein said conversion reaction comprisesthe catalytic dehydrogenation of hydrocarbons.

' 6. The process' of claim l, wherein said conversion reaction comprisesthe catalytic aromatization of hydrocarbons.

' S L. THOMAS.

